1. Field of the Invention
The invention relates to technological improvements in the production of baked products with low wheat content. In particular the invention describes the utilization of transglutaminase compounds for the production of baked products with a wheat content derived from flour of 1 to 50% by weight.
2. Discussion of the Background
Problems with mechanical dough processing and product quality are known to occur during the manufacture of bread with a low wheat content. In dough types made from wheat, vegetable gluten forms a cellular gluten network and develops a protein film throughout the whole dough. No such gluten network is formed in dough with a low wheat content. The lack of a gluten network is the reason why doughs low in wheat content are not as elastic as wheat doughs. Rye doughs in particular, but also doughs made from special flours, are not elastic. These doughs keep the shape they are given and are sticky and plastic. The presence of rye flour or special flour inhibits the formation of vegetable gluten through swelling pentosans which are believed to prevent the formation of gluten strands. The pentosans envelop particles in the dough such as hydrated rye flour by forming a thick glutinous liquid. The larger proportion of soluble compounds in wheat doughs in comparison to doughs with special flours is also thought to contribute to the differences in dough properties. There is no information available about dough formation in doughs containing rye part wheat. However, rye content is the decisive factor in the properties of the dough and the baked product when a dough mixture containing rye is used. For example, in common practice dough is leavened with a rye flour proportion of just 20%. The dough properties of bread dough containing rye part wheat resemble those of unblended rye flour. This leads to the conclusion that in doughs made from rye flour blends, no uninterrupted protein film forms due to the high pentosan content. The lack of such a protein film results in a low consistency of fermentation in bread made from rye flour or rye flour blends. This in turn leads to flat loaves with insufficient loaf volume.
Special flours are flour types which are not usually suitable for making bakable dough. Such special flours, which can be made from other cereal types but also from leguminous or other plants, contain proteins which are not able to form an uninterrupted network because most of the proteins are soluble. For this reason, most of the problems which occur during the manufacture of rye bread are also encountered with other special flours.
An amylase and pentosanase preparation powder (VERON(copyright) HE made by Rxc3x6hm GmbH) has been used for improving the properties of rye dough and special flour doughs. This product has been used for the treatment of high ammylogram rye flours. However, use of this enzyme preparation resulted in a softer dough and noticeably flatter loaves. Hexose oxidase and glucose oxidase have also been used during the production of bread from blended rye flour (e.g. Poulsen, C. H.; Borch Soe: Strong Effect of Hexose Oxidase on the Stickiness of Mixed Rye/Wheat Sour Dough, Helsinki Meeting Dec. 8, 1999 to Dec. 10, 1999, Congress: 2nd European Symposium on Enzymes in Grain Processing). These enzymes achieved reduced dough stickiness. The effect on loaf shape and fermentation is however not described. Furthermore, oxidases are known to react with the carbon hydrates in the flour but not the proteins. Therefore, all attempts utilizing the current state of technology for improving the quality of dough low in wheat have been unsatisfactory.
The present invention relates to the task of providing the means and methods for improving doughs that are low in wheat content. In particular, according to this invention, the extensibility of the dough and its gas retention properties will be improved. Furthermore, the means and methods described in the invention are used to improve the baking properties in automated processing, in particular stickiness. The means and methods described in the invention also improve the quality of the baked product, particularly its volume. The baked products should not show any faulty flavor or properties giving rise to toxicological concern. In addition, the means and methods described in the invention are to be generally recognized as safe from a toxicologic and food regulatory standpoint.
Surprisingly, it was found that the addition of transglutaminase to doughs low in wheat significantly improved the properties of the dough and the baked products derived therefrom. The stickiness of the doughs is reduced so that they can be easily mechanically processed. Because of the improved gas retention in the dough, bread volume is noticeably increased. In addition, the stability of the fermentation in the shaped dough is increased. The final fermentation time can therefore be increased by up to 20%. The resulting baked product will nevertheless exhibit a very good shape. Thus allowing a great deal of flexibility at the bakery.
The present invention relates to both the use of transglutaminase for the production of baked products with a wheat content between 1 and 50% in addition to one or more flours other than wheat flour(s), as well as a method for the production of the corresponding baked products which are characterized by the fact that they include transglutaminase as an enzyme component. The invention further covers a baking flour with a wheat content of 1 to 50% by weight of the flour components further containing a transglutaminase. This baking flour may contain flour made from any type of wheat in its wheat component and any type of non-wheat flour in the non-wheat component. The baking flour may be part of a baking mixture.
The effect of the transglutaminase used in the invention was surprising, as in the past it was assumed that transglutaminases could only be successful with doughs of wheat component greater than 50% (EP 0 492 406). The effect of transglutaminase in wheat dough arises from the generation of new connections between the amino acids glutamine and lysine contained in the flour protein. Because of the high content of pentosans which form a glutinous liquid around the rye flour particles, or of soluble proteins in special flours, it was surprising, and not obvious, that transglutaminase would also have such favourable effects in doughs that are low in wheat.
Doughs covered by the invention contain a wheat proportion of 1-50%, preferably 5-50%, more preferably 10-50% and even more preferably 30-50%, where the percentages refer to weight, with the flour component of the dough being 100%. Throughout this disclosure all ranges and subvalues between the stated ranges are included. Any type of wheat may be used for this wheat component, such as dinkel, durum wheat or low-allergen wheat. The non-wheat flour can be any type of flour which on its own does not possess any, or only insufficient, baking properties. Examples are oat flour, barley flour, maize flour, buckwheat flour, millet flour, rye flour, amarath flour, quinoa flour and other non-cereal flours of plant origin, such as potato flour, soya bean flour or leguminous plant flour. These special flours can be used individually or in combination. The preferred non-wheat flour is rye flour. Combinations of non-wheat flour types which can be used are, for example, barley/oats/rye or oats/buckwheat or rye/potato starch. The proportion of non-wheat flour is 50-99% by weight, preferably 50-95% by weight, more preferably 50-90% by weight, even more preferably 50-70% by weight, in all cases with respect to the flour component, total flour content is 100%. In addition, the dough for the baked product may contain the usual ingredients and spices. The dough is processed in the normal way for producing the intended baked products. These baked products may also be filled.
The dosage for the transglutaminase depends on the properties of the individual flour. An enzyme dose between 5 TGU and 5000 TGU is preferred, more preferred is 10-2000 TGU, even more preferred is 30 to 300 TGU per 100 kg of flour depending on the flour blend and the dough processing.
For example, the dosage for 50% rye flour is 70-100 TGU per 100 kg of flour, for 60% rye flour it is 90-150 TGU per 100 kg of flour, for 70% rye flour is 120-200 TGU per 100 kg of flour, for 80% rye flour is 200-300 TGU per 100 kg of flour. For the special flour types the dosage range is between 100 TGU and 5000 TGU, always for 100 kg flour, but more preferably between 300 TGU and 600 TGU depending on the flour type used. The precise dosage for the flour or flour blend can easily be determined by one skilled in the art by means of simple routine experiments.
The enzyme preparation with transglutaminase activity can, on its own or together with other ingredients, be added at any stage after the grinding of the flour (each flour alone or mixed together) and before the dough processing. The enzyme preparation can also be added to the leaven. The enzyme preparation is preferably added together with the baking ingredients. It is also possible to add the transglutaminase to the baking additives for the appropriate dough types. The dough may also contain other commonly used baking additives such as non-transglutaminase enzymes, e.g. amylases, xylanases, pentosanases, hemicellulases, cellulases, endoglucanases, xcex2-glucanases, phospholipases, lysophospholipases, phytases, phosphatases, lipases, lipoxygenases, oxidases or peroxidases. Furthermore, other commonly used additives used in baking such as swellable types of flour, salt, sugar, emulsifiers, organic acids, like lactic acid and acetic acid, citric acid and tartaric acid, vitamin C, etc. may be added.
In preparing the initial mixed flour of the invention there is no special order of addition of ingredients (wheat flour, transglutaminase, non-wheat flour). However, and as mentioned above, the transglutaminase should not be ground for best results. The phrase xe2x80x9cmixing a transglutaminase, a wheat flour and a non-wheat flourxe2x80x9d includes all orders of addition, meaning that any two can be combined and optionally mixed followed by the addition of the third with mixing, that all these can be combined followed by mixing, that the two may be provided in pre-mixed form and the third added and mixed, etc.
The transglutaminases used as described in the invention are preferably produced by cultures of micro-organisms, e.g. by mould fungi or bacteria. The enzyme may also be of plant or animal origin. Transglutaminases produced recombinantly can also be used. A transglutaminase produced from Streptoverticillium mobaraense, IFO 13819 (as described in U.S. Pat. No. 5,156,956 and EP 0 379 606 B2; both hereby incorporated in their entirety by reference) is preferred.
Doughs made from part rye flour can be produced both by direct and by indirect processing. For direct processing organic acids such as lactic acid, acetic acid or citric acid and/or dried leaven are added. For the indirect processing, in the first stage a dough with unprocessed leaven is used. The dough may, in addition, contain yeast. It is also possible to combine the processing methods.
The results of the baking tests show that the transglutaminase is of no effect on doughs made purely from rye flour (see table 1 in example of control experiment 1). Changes do not become visible in the dough nor in the loaf. When testing blends containing 70% rye flour, a noticeable improvement in the properties of dough and baked product are evident, and the degree of comminution rate is of no relevance (tables 2 and 3). With an enzyme dose of just 200 TGU per 100 kg of flour a very good volume increase of 6 vol. % is reached.
Experiments with different proportions of rye flour show that the loaf volume is noticeably increased by an addition of transglutaminase (table 4). A volume increase of up to 7 vol. % can be achieved. The loaf shape and dough stability is even improved with a rye flour proportion of 80%. The transglutaminase results in a major reduction in the stickiness of the dough. The best results are achieved with a proportion of rye flour between 60 and 70%.
In addition, experiments with both types of dough processing were carried out(table 5 and 6). In both cases the transglutaminase had a very noticeable effect on the properties of the dough and the baked product.
Experiments investigating the effect of the transglutaminase on the fermentation stability are shown in table 7. These results show that the effect of the transglutaminase permits a lengthening in the fermentation time of up to 20%. While loaves without transglutaminase are flat and must be regarded as no longer acceptable, the loaves with transglutaminase showed a very pleasing loaf shape and a high loaf volume.
The combination of transglutaminase with several other typical baking enzymes is described in tables 8 to 10. The combination of the transglutaminases with other enzymes has the advantage that, in addition to the increased loaf volume, the improved loaf shape and the improved dough stability, the pore structure in the crust is improved as well.
In addition, baking tests with special flours were carried out(see tables 11 and 12). The results are similar to those with the bread types made from rye flour blends. Here, again, loaves with very pleasing shapes and high volumes were produced. The dough was also improved. The dough is more easily processed because it is less moist and more elastic.
The transglutaminase activity of an enzyme preparation can be determined by means of the colorimetric hydroxamate test. Here 1 TGU/g is defined as the quantity of an enzyme which under standardized conditions, at 37xc2x0 C. and pH 6.0 with 0.2 M tris-HC1 buffer, releases 1 xcexcmol hydroxyamine acid.
One cellulase activity unit (CU) is defined as the enzyme activity which lowers the viscosity in the preparation with a standard CMC solution in the defined measuring range and under the stated reaction conditions (30xc2x0 C., pH=4.5, t=11 min and volume flow of the reactive solutions) by xcex941*xcex7xe2x88x921=45.11*10xe2x88x926.
xcex941*xcex7xe2x88x921 is the difference between the reciprocal value of the viscosity of the standard CMC solution after being exposed to the enzyme and the reciprocal value of the viscosity of the untreated CMC solution.
The activity concentration unit: CU mgxe2x88x921 
The xylan fragments released by the enzymatic dissociation of xylan are determined photometrically at 412 nm with p-hydroxybenzoic acid hydrazide (PAHBAH). 1 Xy1H unit corresponds to the quantity of enzyme which will release 1 xcexcmol reactive equivalent of xylose by dissociation of xylan within one minute at 30xc2x0 C. under standard conditions.